BULLETIN 195. CALIFORNIA GRAPE ROOT-WORM. 19 



very effective appearing as dependent primarily upon moist weather. 

 The fact that the eggs of this beetle are very securely hidden away 

 beneath one or more layers of bark affords little opportunity for them 

 to be attacked in any large manner by parasitic or predatory insects. 

 The young larva is for a brief period (from the time of hatching until 

 it enters the ground) more or less exposed to the attacks of enemies, 

 but the interval is generally too short to allow of very great destruction. 

 Once in the ground where it remains for the greater part of the year 

 it is pretty safe from most enemies. About the only thing likely to 

 attack the larva here would be the predaceous ground beetles. None 

 of these were actually observed attacking them during the past two 

 years. The larva is usually so deep in the ground as to be out of reach 

 of most natural enemies. 



The pupa comes nearer to the surface and is hence more liable to 

 attack. It is probably in this stage that the greatest mortality occurs, 

 both from enemies arid from cultivation of the soil and other opera- 

 tions by man. In the adult or beetle stage, the insect is directly exposed 

 and is likely to be attacked by a large number of enemies, including 

 insects and birds. 



ARTIFICIAL CONTROL. 



Of the Egg. Since the eggs are secreted under one or more layers 

 of bark, there is little possibility of any spray or wash reaching them. 

 On account of their small size and the difficulty of finding the clus- 

 ters, hand . picking is out of the question. Those who believe in 

 stripping off the old bark and spraying with bluestone during the 

 dormant season, with the primary object of preventing black knot, 

 will, incidentally, inconvenience these beetles by doing away with 

 the more favorable situations for egg laying. This, however, can 

 not be counted upon as very effective in controlling the beetle. The 

 eggs will be deposited in spite of this treatment, and freeing the vines 

 from their loose bark will result simply in rendering the eggs a little 

 more exposed to the attack of enemies. 



Of the Larva. The matter of controlling any underground insect 

 is a difficult problem, and the larva of this beetle is no exception to 

 the general rule. Various remedies and schemes have been tested for 

 accomplishing this work, but the greater number of them have been 

 abandoned. The problem, therefore, is now limited largely to control 

 by resistant stock, cultivation, crop rotation, or other regular farm 

 practices; but, with an insect such as this, that spends a portion of 

 its existence above ground, it is not necessary to control it in the larval 

 stage, since it can be more easily and effectively done in a later stage. 



It was suggested by some of the growers that something might be 



